The invention relates to a support for an assembly for motor vehicles, comprising a crossbeam which is fastened to the body of the assembly, and a supporting plate which is fastened on said crossbeam in a manner enabling it to be detached in the event of a collision, on which the assembly is supported, the supporting plate being connected to the crossbeam at a number of points, and at least part of the assembly being situated upstream of the support in the direction of travel, and comprising a separating device which separates the supporting plate from the crossbeam in the event of a collision.
An assembly is understood to be the drive train or part of it, in particular the engine/transmission block and, if appropriate, an adjoining differential or power take-off gear. These assemblies are virtually all accommodated nowadays in the front end of the vehicle. The crossbeam is a crossrail which connects the longitudinal crossbeams of the vehicle body or of the vehicle frame, depending on the manner of construction of the vehicle. The assembly is supported in respect of forces and moments at three points as a rule, all three being suitable for the support according to the invention, but in particular the rear one.
In the event of a head-on collision, first of all the front end is deformed over a certain deformation distance, decelerating the part of the vehicle body which lies behind it; this part is the cell in which the passengers sit. When the deformation distance has been covered, the assembly strikes against the obstacle. The assembly itself is virtually impossible to deform, and so the deceleration rises very sharply. If the assembly is connected fixedly to the vehicle body, the deceleration of the passengers may reach lethal values. The prior art therefore ensures that the assembly is released from its fastening to the vehicle and is pushed to the rear with further consumption of energy. Moreover, measures still have to be taken so that the assembly is not pushed into the cell, but rather some of it is initially pushed under the cell.
A construction of this type is disclosed in DE 43 18 254 A1. A supporting bearing which can be destroyed in the event of a collision is provided for this. If said supporting bearing is destroyed, the assembly can pivot away downward. The supporting bearing has to be sufficiently strong for it to be able to absorb, in all driving conditions, the forces which are exerted by the assembly and, in the event of a collision, the forces which occur in the first phase—in which only the front end is deformed. One drawback is that the destruction of such a strong supporting bearing requires considerable forces, which causes a brief, but nevertheless steep rise in the deceleration. If the supporting bearing is then destroyed, the further movement of the assembly takes place virtually without any consumption of energy.
It is known from practice to provide, between the supporting bearing and crossbeam, a supporting plate which is connected to the crossbeam and is connected only in a pointwise manner to the crossbeam, by means of bolts, rivets or preferably welding points, so that these connections tear in the event of a collision. However, even this solution is not satisfactory because there is still a discrepancy between the fatigue strengths and force absorption of the connection in the first phase of a collision and the force which is required for tearing-off purposes and which causes deceleration peaks.
Finally, DE 196 36 167 discloses an assembly separation which is caused by a head-on collision and is triggered by a collision with the front bumper. The assembly sits, obviously fixedly, on a auxiliary frame which is connected to the longitudinal crossbeams of the frame via “bearing shafts” which lie longitudinally. In the event of a collision, at least one piston rod, which is connected to the bumper via an elastic element, is displaced to the rear, in which case it pulls the bearing shafts connected to it to the rear. As a result, the connection between the auxiliary frame and the longitudinal crossbeam of the frame is released without significant effort and the assembly should fall to the ground. However, no more mechanical energy is destroyed in the process, and so the existing problem cannot be solved with this.
It is therefore the object of the invention to provide an assembly support in which this discrepancy does not exist, which, in other words, ensures a continuous deceleration profile over as long a distance as possible. Since, however, the deceleration profile is also affected by the mass and deformation work of further components which can be changed to only a very limited extent, the assembly support is intended even to permit modeling of the force profile over the deformation distance in respect of an overall constant deceleration.